Irradiation of materials by energetic particles produces defect clusters like vacancies, self-interstitial atoms and stacking-fault tetrahedra. These defect clusters form loops around existing dislocations, leading to their decoration and immobilization, which ultimately led to radiation hardening in most of the materials. The effect of irradiation upon material shear yield strength was analyzed using two-dimensional polycrystal dislocation dynamics modelling. The plastic flow in the material was represented as collective behaviour of a large number of edge dislocations distributed among many grains. The unit cell was assumed to have grains of hexagonal shape with uniform size. Grain boundaries were considered to be impenetrable to dislocations. The irradiation effects were modelled by taking all dislocations being locked by irradiation defects thus characterizing the fluence. When the total stress on the dislocations exceeds a critical stress value, they get unlocked and became free to move on their glide planes. Typical stress–strain curves for various critical values were obtained for irradiated Aluminium with different grain sizes, which revealed the effect of dislocation loops on increased yield stress as a function of both fluence and grain size. Critical locking stress was correlated to irradiation fluence by using single crystal yield stress values of irradiated Aluminium from dislocation dynamics analysis and corresponding experimentally available yield stress values.

Application of Dislocation Dynamics to Assess Irradiation Effect on Materials with Different Grain Sizes. P.V.Durgaprasad, B.K.Dutta, H.S.Kushwaha, S.Banerjee: Nuclear Engineering and Design, 2011, 241[3], 603-7